With the technology development, a computer becomes an essential electrical appliance for each family. The image quality of the monitor or display for use with the computer is as important as the operation speed and performance of the computer. Since conventional cathode-ray-tube (CRT) monitors are space-inefficient and suffer from high radiation, a liquid crystal display (LCD) has taken the place of the conventional monitors to become the main stem.
Generally, when the LCD panel is operated, a driving circuit is required to perform a scanning operation to store the displayed data into pixels of liquid crystal display (LCD) in sequence. In this driving circuit, a voltage level shifter is used to convert a clock signal at a low voltage level into a clock signal at a high voltage level. Since the peak-to-peak value of the clock signal at the high voltage level is larger than that of the clock signal at the low voltage, level, the clock signal at the high voltage level is more powerful than the low level one to drive the rear-stage circuit and further the LCD panel.
A conventional voltage level shifter includes the combination of the PMOS and NMOS transistors. Therefore, the IC manufacturing process involves both the PMOS transistor process and the NMOS transistor process and thus is very complicated.
Currently, the production of an LCD panel includes one of essentially NMOS, PMOS transistor process and CMOS transistor process. The essentially NMOS and CMOS transistor processes undesirably involves too many masking steps so that the PMOS manufacturing process, so far, is the most popular for producing the LCD panel.
However, even if the LCD panel can be produced by the essentially PMOS transistor process, NMOS transistor process is still required if the voltage level shifter is integrated into the panel. Therefore, the process for producing the combined LCD panel and voltage level shifter is still complicated, and the yield is unsatisfactory.
Therefore, the purpose of the present invention is to simplify the manufacturing process of the combined LCD panel and voltage level shifter to deal with the above situations encountered in the prior art.